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Imagine you’re tasked with building the world’s lightest drone chassis—something strong enough to survive turbulence but light enough to fly longer. You’ve narrowed it down to magnesium alloys. But then comes the question… AZ31B or AZ91D? Which one do you choose?

This isn’t just a metal selection—it’s an engineering decision that affects cost, performance, and even your product’s environmental impact.

Let’s break down these two magnesium marvels.

The Basics: Wrought vs Cast Magnesium Alloys

Magnesium alloys fall into two main categories:

• Wrought Alloys (e.g., AZ31B – UNS M11311): These are formed through mechanical methods such as extrusion and rolling.
• Cast Alloys (e.g., AZ91D – UNS M11916): Produced by pouring molten metal into molds.

Each category influences properties like strength, ductility, and application suitability.

Chemical Composition

Mechanical & Thermal Properties

Machinability & Formability

• AZ31B: Rated as excellent. Best suited for prototyping, complex shapes, and precision work.
• AZ91D:Very good machinability but shines in high-volume die-casting, ensuring dimensional stability and consistency.

Applications: Where They Shine

AZ31B Magnesium Alloy Applications:

Aerospace Components: Lightweight structural parts such as brackets and panels are manufactured using AZ31B to reduce overall aircraft weight and improve fuel efficiency.

Industrial Applications: Commonly used in power tools and mechanical equipment where reduced weight improves operational ease.

Prototypes: Due to its machinability, AZ31B is favoured for rapid prototyping and proof-of-concept designs

AZ91D Magnesium Alloy Applications:

Consumer Electronics: Frequently used for lightweight casings in laptops, smartphones, and cameras, combining strength and reduced weight.

Automotive Components: Widely applied in engine housings, transmission cases, and other parts where weight reduction is critical to vehicle efficiency.

Recreational Equipment: Utilized in the manufacturing of sporting goods such as bicycle frames and golf club heads for their lightweight and durable qualities.

Environmental Considerations

Though AZ91D has slightly higher embodied water and carbon (22 kg CO₂/kg vs 23 for AZ31B), it also offers longer lifespan and greater durability.

✅ Sustainability Takeaway:
Fewer replacements mean less energy spent on recycling and fewer emissions over time. If your product faces tough environments, AZ91D is the more eco-friendly choice.

Standards & Specifications

• AZ31B Magnesium Alloy:
  • ASTM B90/B90M
  • Available in: Plates, Sheets, Rods, Bars, Extrusions
  • Condition: H24 (strain-hardened & partially annealed)
• AZ91D Magnesium Alloy:
  • ASTM B93/B93M
  • Common as: Castings (Die Cast or Sand Cast)
  • Shape: Engine casings, electronic housings, intricate brackets

AZ31B vs AZ91D – Summary Table

🏁 Final Thoughts: Which Alloy Should You Choose?

If your goal is flexibility, forming ease, and fast prototyping, choose AZ31B.
However, if you’re producing in large volumes, need resistance to harsh environments, and want cost-efficient casting, then AZ91D is your best bet.
Whether you’re building the next generation of drones or enhancing vehicle performance, selecting between AZ31B and AZ91D can define your product’s success and sustainability.

 Contact us now to explore custom solutions for your tech.

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